Expansible piston



W. WILSON ExPANsIBLE BIsToN 4Original Filed Aug. 20. 1934 April 5, 1938.

Patented Apr. 5, i938 omer.

Application August 20,

1934, serial No. 740,574

Renewed June 5, 1937 7 Claims.

My invention relatesj to a piston construction and more specifically to expansible pistons for use in internal combustion engines.

It has been found that pistons of internal combustion engines wear in such a Way as to develop piston slap due to the side pressure to which the pistons are subjected. Various devices have been proposed with a view to remedying or lessening the bad eects of this wear, including spring expanders and screw expanders. The spring devices, however, are open to the objection that they cause considerable pressure to be exerted by the piston on the cylinder walls, resulting in excessive wear. kThe screw devices are open to the objection that there is no automatic take-up, so that it is necessary to adjust them from time to time to take up the wear.

One of the objects of my invention is to provide means for exerting pressure to expand the piston, controlled in its pressure-exerting action by wear due to the movement of the piston. This prevents the spring pressure from excessively expanding the piston, thus avoiding the objection to the present spring expanders, and it provides an automatic wear-controlled take-up, thus avoid- This device may be installed in a new motor 'and provides an automatic take-up for the expansible piston during the life of the motor. With the present types of piston expander-s it is necessary to dismantle the motor to install or adjust them.

In the drawing, in which several forins of my invention are shown,f-

Figure 1 is a bottom plan view of a piston and associated parts embodying my invention;

' Fig.v 2 is a sectional view substantially on the line 2--2 of Fig. 1;

Fig. 3 is a detail view showing the wrist pin and associated parts; K s

40 Fig. 4 is a bottom plan viewshowing another l form of piston and associated parts;

Fig. 5 is a bottom view of another form of piston and associated parts embodying my invention;

Fig. 6 is a bottom View of another form of piston and associated parts; and

Fig. 7 is a bottom view of another form of pston and associated parts.

Referring to the drawing in detail, and first to Figs. 1, 2, and 3, the construction shown therein comprises an expansible piston I, which may be of aluminum or other suitable material. a connecting rod 2, and a hollow wrist pin 3 to whichthe upper end of the connecting rod is clamped 55 by means of a screw ii. The wrist pin is mounted ing the objections to the present screw take-up.

for a slight rocking movement in suitable bearing bosses 5 on the piston l.

I take advantage of the wear occasioned by the slight rocking movement of the wrist pin td control the expanding action of the springpressed wedge 6 which engages the inclined surfaces 'l adjacent the split 8 in the' piston and which tends to expand the piston. This wedge 6 may be in the form of a yoke having openings in its side portions 9 through which the rockable wrist pin extends. Suitable helical compression springs IIJ are provided surrounding the pins H formed on the sides of the yoke for exerting pressure to expand the piston. These springs can force the wedge no further than the wrist pin will permit, as the edges of the openings in the yoke engage the wrist pin, thus restraining its wedging action. However, the spring pressure on the yoke will cause a wearing action on the edges of the openings in the yoke so that as the wrist pin rocks, the edges of the openings in the yoke will wear and permit the wedge to move very gradually in a direction to expand the piston. The Wearing action may be controlled, either by cutting away a portion of the edge of the opening on the side toward the spring, as shown at l2 in Fig. 2, or by providing the edge of the opening on the side toward the spring with material having the desired wearing qualities, which will cause just the proper gradual movement of the wedge, as shown at I3 in Fig. 3.

With this construction, it will be seen that the full pressure of the spring is prevented from being exerted as a force tending to expand the cylinder but that the gradual wearing action dueA to the rocking of the wrist pin will allow a very gradual movement of the wedge which will takev up the wear on the piston at a rate proportional to the extent of use of the piston. It will also be seen that there is a compensating action between the wear of the piston itself and the Wear on the edge of the opening in the Wedge due to the wrist pin action, since if the piston wears comparatively rapidly-say, due to poor lubricationthe poor lubrication will at the same time produce increased wear on the expander bearing, thus permitting a comparatively greater rate of expansion than would result with normal lubrication.

The construction of Fig. 4 is quite similar to that just described, except that the expanding action of the piston is effected by a resilient curved plate Ill engaging opposite sides of the split 8 in the piston and that the springs Ii which act on the yoke are backed up by another yoke I5 mounted on'lthe bearing bosses 5 of the piston.

The construction of Fig. 5 is similar to those previously described except that here the springs I I which exert pressure on the yoke I6l are backed up by the bearing bosses on the piston itself and the further -distinction that the bearing bosses' are split, as indicated at I1, thus providing a construction in which the smaller of the split portions Il may yield under the wearing action of the rocking movement of the wrist pin and the spring pressure-exerted on the yoke. This construction will also act to take up for wear in the wrist pin bearing itself.

In Fig. 6 is shown a construction in which the piston is split at diametrically opposed points and. two expanding members I9 are substituted for the expanding yoke of the previous constructions. In this i'orm two spring-pressed pressure-exerting members are provided, each i pivotally mounted on theV piston as indicated at 20, adjacent a split in the piston, each havinga portion through which the wrist pin extends, and each provided with a spring II for exerting an expanding action on the pressure-exerting mem-l ber. Each of these pressure-exerting members is provided with an extension 2I for engagement with a lug 22 on the edge of the split in the piston. 'I'his lug acts as a guide for preventing radial movement.

The construction of Fig. 7 is similar to that of Figure 1 except that in this i'orm the wear takes place on a. bushing 23 of suitable material secured to the wrist pin to rock therewith. In this form, the wear on the bushing permits the slow graduated movement of theexpanding wedge B under the action of the 'springs I I. In this form the yoke is shown as made in two parts spaced from each other as indicated at 23* and having provisions for adjustably spacing the parts of the yoke. The means shown for this purpose comprise 'a screw 23h having an enlarged portion 23 threaded into one side of the 'yoke and having a reduced portion 23d swivelled in the' other side of the yoke. With this construction the yoke members may be adjusted to the desired spaced position and may be held in this position by means of a lock nut 23. This adjustment may be specially useful when the expander is being applied to a worn piston as it enables the repairman'to adjust the yoke to secure proper relation between the piston and cylinder.

Having thus described the invention, what is claimed as new and is desired to secure by Letters Patent is:

' 1. A piston construction comprising an expansible cylindrical piston for operating in a cylinder, awrist pin rockably mounted with respect to said piston, means exerting force to expand said piston. and wearable means controlled in its action by wear accompanying the rocking movement of said wrist pin preventing the force of said force-exerting means from being exerted to such a distance as to press the piston against the cylinder wall but enabling a slow restrained movement of said force-exerting means as the wear progresses.

2. A piston construction comprising an expansible cylindrical piston for operating in a cylinder, a wrist pin rockably mounted with respect to said piston, spring means exerting force to expand said piston, and wearable means controlled in its action by wear accompanying the rocking movement of said wrist vpin preventing the force of said force-exerting means from being expand said piston, and wearable means controlled in its action by wear accompanying the rocking movement of said wrist pin preventing the force of said force-exerting means from being exerted to such a distance as to press the piston against the cylinder wall but enabling a slow restrained movement of said force-exerting means as the wear progresses, said force-exerting and wearable means comprising a force-transmitting member having an opening through which said wrist pin extends, said spring means exerting force on said force-transmitting member to cause wear' on the edges of said opening due to the rockingl movement of the wrist pin.

4. A piston construction comprising an expansible cylindrical piston for operating in a cylinder, a wrist pin rockably mounted with respect to said piston, a connecting rod secured to said wrist pin, spring means exerting force to expand said piston, and wearable means controlled in its action by wear accompanying the rocking movement of said wrist pin preventing the force of said force-exerting meansfrom being exerted to such a distance as to press the piston against the cylinder wall but enabling a slow restrained movement of said force-exerting means as the wear progresses, said force-exerting and wearable means comprising a pair of force-transmitting members straddling said connecting rod and having openings through which `said wrist pin extends, said spring means exerting force on said force-transmitting members to cause wear on the edges of said openings due to the rocking movement of said wrist pin.

5. The combination of a piston having an expansible skirt, a. member mounted in said skirt and being free to oscillate therein, an expander element having a portion thereof in wear-engaging relationship with said member and having another portion engaging said expansible skirt, and resilient means engaging said expander element to urge the same into engagement with said skirt as said expander element wears in use.

6. In a piston having an expansible skirt, means mounted therein in free oscillating relationship thereto, other means contacting said expansible skirt and arranged in wear-engaging relationship with said first-mentioned means; and resilient means engaging said second-mentioned means and tending to preserve said contacting relationship as said second-mentioned means wears in use.

7. An expanding piston construction comprising a piston having an expansible'skirt, a member carried by said piston mounted for relative movement with respect thereto, expansion-controlling means in wear-engaging relationship with respect to said movable member and in expansioncontroliing relationship with respect to said ex,- pansible skirt, said expanding piston construction having means for urging said expansion-controlling means into wear-engaging relationship with said lmovable member and into expanding relationship with respect to said expansible skirt.

WESLEY WILSON. 

